The invention relates to liquid-crystalline nematic mixtures functioning in electro-optical arrangements to modulate transmitted or incident light as well as to reproduce numbers, signs and images, and to methods for their preparation.
It is known that electro-optical arrangements for the modulation of light may be produced with the aid of appropriate nematic liquid-crystalline substances and that the same substances also serve to reproduce numbers, signs and images. Nematic liquid crystal with positive dielectrical anisotropy especially allow for the construction of rotary cells or cells based upon the guest-host effect (M. Tobias, International Handbook of Liquid Crystal Displays 1975-1976, Ovum Ltd. London 1976).
Substances of high positive dielectrical anisotropy are needed in order to obtain low swelling and working potentials, particularly advantageous with battery activated devices. The melting and clarification points of the substances used are also extremely important because they determine the range of operating temperature of the components. Due to the fact that there are no substances presently known which possess the combination of the relatively high clarification point required and also of a sufficiently low melting point, mixtures are exclusively used where lowering of the melting point of multi-component systems is utilized. In order to be able to accommodate the mixtures to various requirements, suitable substances are needed as components and a constant search is carried on for new appropriate compounds.
The object of the invention is liquid-crystalline compounds having high positive dielectrical anisotropy and high clarification points, as well as methods for their preparation.